The present invention relate s to an apparatus and method for detecting a condition of a vehicle and, more particularly, to an apparatus and method for sensing a condition of a vehicle tire.
Numerous tire pressure monitoring systems have been developed in order to detect when the air pressure within a tire drops below a threshold pressure value. These systems typically include a pressure switch, an internal power source, and a communications link that provides the tire pressure information from a location at each vehicle tire to a central receiver, which may be mounted on the vehicle dashboard. The communications link may be a wired or wireless link.
There has been a n increasing need for tire pressure monitoring systems due to the Use of xe2x80x9crun flatxe2x80x9d tires in vehicles. These xe2x80x9crun flatxe2x80x9d tires enable a driver to travel an extended distance after the loss of air pressure within the vehicle tire.
Tire pressure monitoring systems are becoming increasingly complex and are requiring the use of numerous circuit components to achieve desired monitoring characteristics. Examples of tire pressure monitoring systems are disclosed in U.S. Pat. No. 5,285,189, U.S. Pat. No. 5,335,540, U.S. Pat. No. 5,055,826, U.S. Pat. No. 4,311,985, U.S. Pat. No. 5,061,917 and PCT International Application No. PCT/US94/13271.
The present invention is directed to a tire condition sensor module for a vehicle that includes a tire condition sensor operative to sense a condition of an associated vehicle tire and provide a tire condition signal having a characteristic indicative thereof. A motion detector is operative to detect movement of the associated vehicle tire and provide a motion signal having a characteristic indicating movement of the associated vehicle tire. The sensor module also includes a transmitter which is operative to transmit a tire transmitter signal having a characteristic based on the tire condition signal. A controller has one operating mode responsive to the motion signal in which the controller controls the transmitter to intermittently transmit the tire transmitter signal. The controller has another operating mode, also responsive to the motion signal, in which the controller controls the transmitter to transmit the tire transmitter signal only after the controller determines that the tire condition signal indicates that the sensed tire condition is either above or below a first predetermined tire condition threshold. The controller also controls the tire condition sensor to sense the tire condition of the associated vehicle tire during each of the operating modes.
Another embodiment of the present invention is directed to a method for monitoring a condition of a vehicle tire. The method includes the steps of detecting movement of the vehicle tire and providing a motion signal indicative of detected movement. It is determined whether the motion signal indicates movement of the associated tire. A sensor is periodically activated to sense a condition of the vehicle tire and a tire condition signal having a characteristic indicative thereof is provided. Tire condition data based on the tire condition signal is intermittently transmitted when the motion signal indicates at least a first amount of detected movement. When the motion signal has a characteristic indicating less than the first amount of detected movement, the tire condition data is transmitted only after determining that the tire condition signal indicates the sensed tire condition is either above or below a first predetermined threshold.